The objective of this research is to develop and study nonhuman primate models of strabismus. Four specific monkey models are proposed: 1) surgical, 2) optical, 3) neurotoxin, and 4) natural. Each monkey model will be tested behaviorally to determine what impairments in visual functions result from the strabismus. Specific impairments to the looked for are amblyopia and loss of binocular stereoscopic vision. Experiments are designed to determine both the magnitude of any impairments and also the time course over which they develop. These measurements will be used to provide information about the "sensitive period" associated with strabismus. Macaque monkeys are chosen as the model species because information about sensitive periods can be extrapolated to humans with more confidence than from any non primate model.